1. Field of the Invention
This invention relates to a capping unit suitable for use in a recording apparatus having an ink-jet recording head which is moved in the width direction of a recording sheet, and forms images on the recording sheet or the like by jetting ink droplets according to print data.
2. Description of the Related Art
An ink-jet recording apparatus records print data on a recording sheet or the like by jetting ink droplets from nozzle openings while ink is pressurized in pressure generating chambers. However, such an ink-jet recording apparatus has potential inconveniences resulting in poor printing quality due to an increase in ink viscosity caused by the evaporation of an ink solvent from the nozzle openings, the solidified ink and dust sticking to the nozzle openings and the penetration of air bubbles therethrough. Therefore, the ink-jet recording apparatus is normally provided with a capping means for sealing up the nozzle openings of a recording head during the non-printing operation and a cleaning means for cleaning a nozzle plate, if necessary.
For example, as disclosed in Unexamined Japanese Patent Publication No. Hei. 6-8460, there has been proposed a capping unit having a cap which is pressed by a recording head or a carriage for carrying the recording head to move between a non-capping position and a capping position, the capping unit being placed outside a printing area, a cam face and a cam follower for moving the cap to the side of a nozzle plate of the recording head while the recording head is kept moving from the non-capping position to the capping position.
According to the arrangement above, the carriage is only moved whereby to ensure that it is brought into resilient contact with and seals up the nozzle plate. However, the number of nozzle openings of a black recording head for jetting black ink in order to meet high-density, high-speed printing requirements and the number of nozzle openings of a color recording head for jetting three kinds of colored ink tend to increase. As the size in the paper feeding direction and the size in the width direction of paper grow larger, the size of the cap for sealing up each recording head becomes inevitably larger and the inconvenience is that the sealing capability is lowered.
Moreover, the ink penetrated between the cap and the recording head is set up because of the use of quick-drying ink and the like, thus causing the cap to rigidly stick to the recording head, and this develops the problem of necessitating a strong force of separating the cap therefrom.
Further, there is another problem arising from a decrease in sealing strength as the sealing surface varies with the head-to-head tolerance and so forth because a platen gap is caused to greatly fluctuate when characters are printed on various printing media.
There is still another problem developing from the residual ink staying and setting up at the recording head when an attempt is made to form a thin-wall portion on the open face to secure a sealing condition by decreasing the elasticity of the cap in order to solve the problems mentioned above.
On the other hand, a tube pump is employed for a pump unit for filling the recording head with ink and supplying negative pressure to the cap at the time of cleaning in view of cost and reliability and besides part of the tube used to form the pump is directly used as a connection channel with the cap. Therefore, there still exists another problem resulting from great repulsive force of the tube, which acts as what impedes the adhesion of the cap, thus reducing the adhesion thereof because such a tube has to be placed in a limited space and is made of relatively rigid material so as to resist against the pressure applied by a roller while functioning as a pump tube.